Objective Updating of Design Predictions for Supported Excavations Using Construction Monitoring Data

点击翻译按钮获取中文摘要

A major concern when performing deep excavations in urban environments is the impact of construction-related ground movements on adjacent buildings and utilities. Given the uncertainties associated with making movement predictions, it is usual to include a monitoring program to record the ground movements that develop during construction. Ideally, these recorded movements can be used to control the construction process and update predictions of movements given the measured deformations at early stages of constructions. However, it is quite difficult, if not impossible, to use the observed movements for these purposes in a timely enough fashion to be of use in a typical project where time is of the essence to a contractor. To improve the state-of-the-art of predicting and controlling ground movements associated with supported excavations, this project develops methods to (1) objectively update design predictions of deformations for supported excavations in clay using monitoring data obtained during construction, and (2) to evaluate critical inputs to performance predictions in design. Automated procedures, such as inverse modeling techniques, are adopted wherein a given model is calibrated by iteratively changing model input values until the simulated output values match the measured data. These procedures will be coupled with a finite element program to automatically update predictions of ground movements. Objective measures of the critical inputs to a finite element analysis of a supported excavation are developed to provide quantitative information concerning the relative importance of various input parameters. The Infrastructure Technology Institute has provided funding to help support this effort. The methodology is developed and tested using detailed ground and building movement data from a 13 m deep excavation through soft clays for a subway renovation project in Chicago. With funding from Wiss, Janney, Elstner Associates through the Chicago Department of Transportation, Northwestern University collected and analyzed ground deformations and adjacent building movements at the subway excavation. An advisory committee comprised of an owner's representative and geotechnical and structural designers provides input to the project via periodic reviews of the progress of the work. Members of the advisory committee also contribute detailed case studies from their project files that are used to check the methodology initially developed based on the data from the Chicago project.